Seasonal variation of dimethyl sulphide in the North Sea and an assessment of fluxes to the atmosphere

The distribution of DMS concentrations in surface waters of the southern North Sea is described for nine months (February-October) in 1989. Minimum concentrations in winter were 0.13 nM and the maximum, monthly mean concentration was 25 nM, in May, coincident with large blooms of Phaeocystis pouchetii, off the continental coast. Comparison with other North Sea data suggests that the interannual seasonal pattern of DMS concentrations is similar. Transfer velocities, for sea-to-air transfer of DMS are derived, comparing a number of methods, and some of the uncertainties in the flux calculation are discussed. Optimised flux data for the North Sea show a distinct annual cycle with monthly averages ranging from 0.2 to 16.4 µmol m-2 day-1 for February and June, respectively. Comparison with other data suggests that North Sea fluxes are very similar to other ocean areas in a similar latitude band and on an annual and seasonal basis. The potential impact of North Sea DMS fluxes on the European atmospheric sulphur budget is discussed.